Confused about Coordinates in D3

Here’s the code:

<body>
  <script>
    const dataset = [
                  [ 34,    78 ],
                  [ 109,   280 ],
                  [ 310,   120 ],
                  [ 79,    411 ],
                  [ 420,   220 ],
                  [ 233,   145 ],
                  [ 333,   96 ],
                  [ 222,   333 ],
                  [ 78,    320 ],
                  [ 21,    123 ]
                ];


    const w = 500;
    const h = 500;

    const svg = d3.select("body")
                  .append("svg")
                  .attr("width", w)
                  .attr("height", h);

    svg.selectAll("circle")
       .data(dataset)
       .enter()
       .append("circle")
       .attr("cx", (d, i) => d[0])
       .attr("cy", (d, i) => h - d[1])
       .attr("r", 5);

    svg.selectAll("text")
       .data(dataset)
       .enter()
       .append("text")
       // Question relates to code below

       .attr("x", (d) => d[0] + 5)
       .attr("y", (d) => h - d[1])
       .text((d) => (d[0] + ", " + d[1]))

        // Question relates to code above
  </script>
</body>

I’m confused as to why d[0] + 5 would affect the position of the label and not affect the value itself. For example, why wouldn’t the first three data points in dataset be 39, 114, 315?

Because you’re applying the modification to the text element, not the circle element.